1. Field of the Invention
This invention relates to the production of thinned semiconductor wafers which are made from thick (100 μm to 700 μm) wafers that are thinned from the backside (or potentially front side) only in selected regions.
2. Description of the Previously Published Art
There are several companies that are attempting to make Insulated Gate Bipolar Transistors (IGBTs) that have a semiconductor wafer thickness between 100 μm and 200 μm. The main problems in making these devices in a manufacturing environment are wafer warpage, wafer breakage, and difficulty of using automated equipment.
There are devices where it would be desirable to have power devices with a total thickness of 25 μm. These power devices include fast recovery 200V PN junction rectifiers and MOSFETs. However, semiconductor wafers that are thinned to 25 μm would be extremely difficult to manufacture.
A new technology of Deep Reactive Ion Etch has been recently been developed. Semiconductor processing tools utilizing this technology can achieve etching rates of 10 μm per minute with trench aspect ratio approaching 100:1. Thus, deep, relatively narrow (5-20 μm wide) trenches can be etched entirely through the thickness of a semiconductor wafer. This technology has been used for microelectromechanical systems (MEMS) such as microsensors and microactuators However, for the application to power devices as described in this disclosure, only a partial etch through the thickness of the wafer is used.